The present invention relates to restrictor means for heat pumps of the type comprising a compressor, condenser, evaporator refrigeration system in which refrigerant is compressed by the compressor, condensed in a heat exchanger functioning as the system condenser, and is then passed through a restrictor to a heat exchanger functioning to evaporate the condensed refrigerant and in so doing absorbs heat from the walls of the heat exchanger, after which the evaporized refrigerant is returned to the compressor.
It has been common practice to provide heat pump systems of the type referred to which include means for reversing the direction of flow of refrigerant from the compressor through the two heat exchangers so that the functions of the heat exchangers are reversed. Thus, one of the heat exchangers is adapted to heat or cool the air of a room, for example, according to the direction of flow of refrigerant. When the direction of flow of refrigerant is reversed, it is necessary to alter the degree of restriction between the two heat exchangers to provide for proper operation of the system in the alternative function, as is well understood in the art. Altering the degree of restriction relative to the direction of flow of refrigerant is necessary since a system optimized for cooling generally has insufficient restriction to provide optimum performance when operated to supply heat. That is, in a system optimized for cooling, the compressor will normally circulate refrigerant through the evaporator faster than the surface can evaporate the refrigerant when the system is operated in the heating cycle. The compressor in the heating cycle then pumps unevaporated refrigerant and the system efficiency is low. To overcome this, variable restriction systems have been employed in heat pump refrigeration systems. In many instances, two restrictors have been provided together with parallel valve systems, each of which is adapted to function in accordance with the direction of refrigerant flow.
It is, accordingly, an object of the present invention to provide a simple and inexpensive, yet effective, means to produce a relatively high restriction to the flow of refrigerant from one heat exchanger to the other during the heating cycle, and to produce a substantially lesser degree of restriction when the refrigerant flow is in the opposite direction between the heat exchangers during the cooling cycle.